When working on an image with multiple layers, how can I apply a new adjustment layer to a particular layer or a selection of layers without affecting every layer below the new adjustment layer?
#1
One way is to place the adjustment layer above the target layer and option-click the line between the two layers
#2
A good way is to click on the layer you want to affect, then go to the layer flyout and choose 'new group from layers' (choosing 'normal' instead of the default 'pass through'), you will get a new group with the target layer in it, then you can add an adjustment layer inside the group which will only affect that group.
If you don't pick 'passthrough' it will affect every layer below...
#3